[OpenAFS] Streaming windows media?

Jeffrey Hutzelman jhutz@cmu.edu
Fri, 30 Mar 2007 00:07:53 -0400

On Friday, March 23, 2007 10:30:42 AM -0400 Jeffrey Altman 
<jaltman@secure-endpoints.com> wrote:

> Robbie Foust wrote:
>> Hi,
>> Has anyone ever set up a Windows Media Server to point to content in AFS
>> using the windows client?  Just wondering how well that would work or
>> how reliable it would be.  I know the windows client is *much* more
>> stable now than it has been in the past.  Our other option is to connect
>> the servers to a san (which we already have).
> The question is how much bandwidth do you require and how large a cache?
> The 32-bit Windows client is limited to about 1GB of cache.  For a media
> server you probably want a much larger cache.  The 64-bit Windows client
> can support much much larger caches provided you have enough RAM on the
> machine.  I've tested with a 12GB cache on a machine with 1GB of RAM.
> I know there are problems at 20GB on a 1GB machine because the swapping
> is too great.  However, a 60GB cache on a machine with 8GB RAM should
> work quite nicely.

Actually, cache size is probably not as much an issue here as you might 
think.  What is interesting is

(1) how fast you intend to send data to clients, and
(2) how much pre-buffering you're doing as compared to the AFS chunk size.

When you read a chunk that is not cached, you will have to wait for the 
entire chunk to be received from the fileserver before you will get to do 
any processing on it.  In addition, AFS does not do any sort of automatic 
read-ahead, so cold-cache reads will be rather bursty, requiring more 
pre-buffering and/or extra effort to achieve a continuous transfer.

-- Jeff